A digital image capturing system utilizes an image optic mechanism such as a lens module to form an image, and an image sensor to capture the image. Conventionally, in order to protect the image sensor from oxidation or contamination, the image sensor is sealed in a structural package. The lens module is set on the image sensor package, and directs imaging light to be projected onto the image sensor.
FIG. 1 illustrates a conventional digital still camera module 10. The camera module 10 is constructed to include an image senor package (not labeled), and a lens module 15 covering the image sensor package. The image sensor package includes a substrate 11, an image sensor chip 12, a plurality of bonding wires 13, an adhesive means 14, and a connecting device 16. The substrate 11 has a top side (not labeled), and defines a receiving chamber 110. The top side defines an opening in communication with the receiving chamber 110. The top side is provided with a plurality of connecting pads (not shown) arranged around the opening. The connecting device 16 includes a plurality of metal leads 16a. Each of the metal leads 16a has one end 16b electrically connected to the corresponding connecting pad at the top side of the substrate 11, and another end 16c extending to an exterior of the substrate 11 and bent into a predetermined shape. The image sensor chip 12 is mounted in the receiving chamber 110. The image sensor chip 12 is provided with a plurality of connecting pads respectively electrically connected to the connecting pads of the substrate 11 by means of the bonding wires 13. The adhesive means 14 is applied on areas where the bonding wires 13 connect with the connecting pads of the substrate 11. The lens module 15 defines a through hole 15a aligned with the image sensor chip 12, and includes at least one lens 15b mounted in the through hole 15a. The lens module 15 is fixed to the image sensor package by means of the adhesive means 14, thereby covering the opening of the top side of the substrate 11. In order to mount the camera module 10 onto a circuit board, tin solder is applied to the ends 16c of the metal leads 16. The image sensor chip 12 is thereby electrically connected to the circuit board.
For the camera module 10, it is generally difficult to predetermine and control the amount of adhesive means 14 to be applied between the lens module 15 and the substrate 11. If the adhesive means 14 is insufficient, the lens module 15 may not securely adhere to the substrate 11. Over a period of time, cracks or gaps may occur at the interface between the lens module 15 and the top side of the substrate 11. If this happens, moisture may infiltrate into the receiving chamber 110, thereby adversely affecting the performance of the image sensor chip 12. In addition, the lens module 15 is liable detach from the substrate 11. This may cause complete damage of the camera module 10. Furthermore, if the adhesive means 14 is overly applied, the excess adhesive means 14 is liable to overflow down along an outside wall of the substrate 11 to the bottom of the substrate 11. If this happens, the overflowing adhesive means 14 may form insulating coatings on the ends 16c of the metal leads 16. This may cause the substrate 11 to be unable to properly electrically connect with the circuit board. In either case of too little or too much adhesive means 14, the quality and/or reliability of the camera module 10 may be degraded.
Furthermore, during assembly of the camera module 10, it is difficult to ensure that the lens 15b is precisely aligned with a center of the image sensor chip 12 when mounting the lens module 15 onto the substrate 11. In general, a central part of an image projected on an image pickup surface of the image sensor chip 12 has a higher resolution, while a peripheral part of the image is generally somewhat distorted. In addition, only the central part of the image is generally picked up and presented in a viewfinder. In cases where the optical axis of the lens 15b is somehow displaced from the center of the image pickup surface of the image sensor chip 12, the distorted image will be projected onto the central part of the image pickup surface of the image sensor chip 12. If this happens, the presented image may have reduced quality.
What is needed, therefore, is a digital still camera module having high quality imaging and a reliable, durable structure.